NO NO NO!! He is not alive!!!!!!!! i agree with just about everything people have said; he was in the bathtub, dead, he's not coming back!
and also, that would be WAY too much of the same thing of dead people coming back alive. i mean, emily sloane was dead, she came back alive. allison/francie was dead a couple of times, and she came back alive. i mean "came back alive" for both of them. but also those people had storylines and major parts in the show so it wasn't too big of a surprise to see them again.
with danny, it's been 4 or 5 years (in the show, counting the two years sydney was gone) since he died, and he would have made a reappearance long before IF he was ever coming back.
it would be way too confusing also to have him back because barely anyone would recognize him!! i haven't even seen the pilot, but i have seen a lot of clips from it and read a bunch of summaries, but i for sure wouldn't recognize him unless sydney or someone said, "Danny!" and if he was alive i'm sure all we would see is him wandering around doing spy stuff or something, not a big reunion with sydney.
but he isn't coming back! he's DEAD!!
ok sorry if i'm too passionate...that's my opinion...and everyone else is free to think whatever they want to!!!